If $2a + 9b + 6c = -2$ and $7x + 7y = 3$, what is $90b + 20a - 28x + 60c - 28y$ ?
Answer: $= 20a + 90b + 60c - 28x - 28y$ $= (10) \cdot (2a + 9b + 6c) + (-4) \cdot (7x + 7y)$ $= (10) \cdot (-2) + (-4) \cdot (3)$ $= -20 - 12$ $= -32$